Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/347—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups
  • C07C51/377—Preparation of carboxylic acids or their salts, halides or anhydrides by reactions not involving formation of carboxyl groups by splitting-off hydrogen or functional groups; by hydrogenolysis of functional groups
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
  • C07C51/44—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation by distillation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
  • C07C51/42—Separation; Purification; Stabilisation; Use of additives
  • C07C51/487—Separation; Purification; Stabilisation; Use of additives by treatment giving rise to chemical modification
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C57/00—Unsaturated compounds having carboxyl groups bound to acyclic carbon atoms
  • C07C57/02—Unsaturated compounds having carboxyl groups bound to acyclic carbon atoms with only carbon-to-carbon double bonds as unsaturation
  • C07C57/03—Monocarboxylic acids
  • C07C57/04—Acrylic acid; Methacrylic acid
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/30—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
  • C07C67/317—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by splitting-off hydrogen or functional groups; by hydrogenolysis of functional groups
  • C07C67/327—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by splitting-off hydrogen or functional groups; by hydrogenolysis of functional groups by elimination of functional groups containing oxygen only in singly bound form
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/48—Separation; Purification; Stabilisation; Use of additives
  • C07C67/52—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation
  • C07C67/54—Separation; Purification; Stabilisation; Use of additives by change in the physical state, e.g. crystallisation by distillation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/48—Separation; Purification; Stabilisation; Use of additives
  • C07C67/60—Separation; Purification; Stabilisation; Use of additives by treatment giving rise to chemical modification
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
  • C07C69/52—Esters of acyclic unsaturated carboxylic acids having the esterified carboxyl group bound to an acyclic carbon atom
  • C07C69/533—Monocarboxylic acid esters having only one carbon-to-carbon double bond
  • C07C69/54—Acrylic acid esters; Methacrylic acid esters

Definitions

• the present invention relates to an improved process for regenerating, by thermal cracking, a mixture of heavy by-products (residues) from an acrylic acid production unit and an acrylic ester production unit, resulting in in obtaining acrylic acid (AA), acrylic esters (EA) and alcohols, with a view to their recycling in the workshop for the production of the acrylic ester.
• the main factor limiting the efficiency of the regeneration of compounds derived from the Michael reaction contained in the heavy flows of the AA and acrylic ester workshops is the increase in the viscosity of the heavy residue obtained at the bottom of the cracker, when the fraction rich in acrylic monomers and alcohol generated by the cracking was vaporized.
• the cracking and vaporization of the light compounds generated are carried out in a reactor, then the gas stream generated is sent to a distillation column and finally the bottom stream of the distillation column is recycled into the reactor.
• the light fraction obtained by cracking being mainly composed of AA acrylic and ester monomers, which are particularly sensitive to polymerization
• the distillation step must necessarily be carried out under reduced pressure, so as to reduce the temperature, to avoid the polymer formation in the column.
• the rectification plates of the distillation column cause the efficient separation of the polymerization inhibitors entrained in the gas mixture, which flow back to the bottom of the column, and therefore, it is necessary to introduce fresh polymerization inhibitors into the gas mixture.
• the efficiency of regeneration depends essentially on two parameters: the temperature and the reaction residence time. Increasing these two parameters tends to improve regeneration efficiency, but this comes at the expense of increasing the viscosity of the cracking residue.
• steps i) and ii) are carried out at the same absolute pressure, between 200 and 2000 hPa, preferably between 300 and 1500 hPa.
• said method comprises the following characters, if necessary combined.
• the partial condensation operation is carried out in an exchanger (condenser) causing the condensation of part of the vapor generated during thermal cracking, without this vapor being subjected beforehand to fractionation in a column. distillation containing one or more rectification plates.
• an exchanger condenser
• the temperature of the gas mixture (overhead flow) leaving the partial condensation step is between 140 ° C and 180 ° C.
• the cracking temperature is between 140 and 260 ° C, preferably between 180 and 210 ° C.
• the residence time of the reaction mixture in the cracking reactor is between 0.5 h and 10 h, preferably between 2 h and 7 h.
• the flow from the bottom of the reactor (residue) obtained at the end of the thermal cracking operation has a dynamic viscosity of less than 1 Pa.s, measured at a temperature of 100 ° C for example at the using a "CAP 1000+” Brookfield viscometer of the cone - plane type.
• the bottom flow of the partial condenser is at least partly recycled into the reactor.
• the liquid flow at the bottom of the partial condenser is recycled directly into the liquid phase of the reactor, by dip tube in the reactor, or in a recirculation pipe for the reaction medium through an external exchanger, preferably upstream of this external exchanger.
• the non-condensed gaseous overhead stream issuing from the partial condenser, rich in AA, acrylic ester and alcohol, is recycled to an acrylic ester manufacturing unit, preferably in liquid form, after condensation in a second condenser.
• the mass ratio of the condensed flow / gas flow entering the condenser is between 5% and 50%, preferably between 10% and 40%.
• the LAA / LEA mass ratio is between 3/7 and 9/1, preferably between 1/1 and 9/1.
• said radical R is a C1-C4 alkyl group.
• the ester is ethyl acrylate and the alcohol is ethanol.
• said regeneration process is operated in continuous mode.
• polymerization inhibitors are introduced at the level of the partial condenser and, when it is used, at the level of the second condenser.
• These inhibitors are chosen from the polymerization inhibitors known to those skilled in the art: phenolic derivatives such as hydroquinone and its derivatives such as methyl ether of hydroquinone, 2,6-di-terbutyl-4- methyl phenol (BHT), and 2,4-dimethyl-6-terbutyl phenol (Topanol A), phenothiazine and its derivatives, manganese salts, such as manganese acetate, thiocarbamic or dithiocarbamic acid salts , such as metal thiocarbamates and dithiocarbamates, such as copper di-n-butyldithiocarbamate, N-oxyl compounds, such as 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (4-OH-TEMPO), compounds containing nitroso groups, such as N-nitro, such
• the thermal cracking reaction takes place in the absence of a catalyst.
• the thermal cracking reaction takes place in the presence of catalysts.
• catalysts mention may be made of Broensted acids, such as sulfuric acid, sulfonic acids, phosphoric acid, zeolites, aluminas or catalysts based on silica and alumina, Lewis acids such as for example titanates, bases, alkali metals or their salts, amines, phosphines, or their combination.
• the present invention overcomes the drawbacks of the state of the art. It more particularly provides a simplified process for thermal cracking of a mixture of heavy by-products originating from a unit for the production of acrylic acid and heavy by-products. from an acrylic ester production unit, making it possible to efficiently recover valuable monomers in the manufacture of acrylic ester. This is accomplished by combining a step of thermal cracking of said mixture, and a step of partial condensation of the overhead stream resulting from the cracking, the two steps being carried out at the same pressure.
• the process for cracking heavy compounds of AA and EA units according to the invention makes it possible to obtain good upgrading yields, regardless of the fluctuations in flow rates and ratios of heavy AA and heavy EA.
• FIG. 1 schematically represents an embodiment of an installation according to the invention.
• FIG. 2 schematically represents another embodiment of an installation according to the invention.
• carboxylic acid addition derivatives formed as by-products of acrylic acid (for example acetic acid) or of water on the double bond of GAA or of the oligomers mentioned above.
• partial condensation refers to an operation during which the gas stream generated during the thermal cracking step is partially condensed in the form of a liquid stream.
• partial condenser refers to equipment making it possible to generate a liquid fraction (reflux) from a hot vapor stream, by cooling on a wall cooler than the vapors. It is generally a heat exchanger kept cooler than the vapors by the circulation of a refrigerant fluid.
• the refrigerant fluid can be for example a gaseous flow, such as air, water, or any other liquid flow coming from an external input to the process or recycled from a process flow.
• the temperature of the vapors leaving the exchanger is regulated to the desired temperature to obtain a more or less significant flow of liquid by partial condensation, by modifying the temperature and the flow rate of the refrigerant liquid in contact with the wall in the partial condenser.
• tube and shell exchangers consisting of a shell and a bundle of tubes inside, in which the two fluids (vapors generated in the reactor and refrigerant) circulate separately. Mention may also be made of spiral exchangers or plate exchangers, or any other type of exchanger known to those skilled in the art and allowing the partial condensation of vapors. These exchangers can be horizontal or vertical equipment.
• total condensation or “total condenser” refer to an operation or equipment carrying out a condensation of the condensable compounds contained in the condensers. non-condensed vapors at the outlet of the partial condenser, in the form of a liquid (distillate) which is withdrawn.
• the invention is based on a thermal cracking process, coupled with a partial condensation operation, the two stages being carried out at the same pressure.
• the process of the invention applies to the regeneration of acrylic monomers from a mixture of heavy by-products originating from an acrylic acid production unit and heavy by-products originating from a production unit. of acrylic ester, and makes it possible to efficiently recover these valuable monomers in the manufacture of the acrylic ester.
• a mixture of streams originating from workshops for the production of acrylic acid (LAA) and acrylic ester (LEA) is introduced in continuous mode in liquid form into the reactor R
• This mixture (1) is rich in heavy compounds derived from Michael's addition generated during the steps of synthesis and purification of the corresponding monomers (AA and EA), and also contains other heavy compounds accumulated during the synthesis processes and purification, in particular polymerization inhibitors.
• the mixture (1) is introduced into the reactor, where it is heated to the temperature required to carry out the cracking of the Michael addition derivatives into lighter compounds which are extracted in the form of a gas mixture (2) at the head of reactor.
• This gas flow is sent to a partial condenser El consisting, for example, of a shell and tube exchanger.
• Said exchanger is circulated by water at a temperature and with a flow rate suitable for cooling the steam to the required temperature, measured in the flow (3) of non-condensed steam leaving the exchanger, and for obtaining the ratio of condensation desired.
• This flow of uncondensed vapor rich in valuable compounds (AA, ester, alcohol) and containing a few heavy compounds in low concentration, is advantageously recycled in the process for the production of the EA ester, either directly in vapor form, or after total condensation. in an E2 exchanger. In the latter case, it is a liquid stream (4) which is recycled to the EA ester production unit.
• a liquid flow (5) (also called reflux) is recovered which is richer in heavy compounds, in particular 3-alkoxy-propionic Michael derivatives, the boiling point of which is intermediate between that of the monomers and those heavier compounds, and also containing some polymerization inhibitors.
• This flow (5) is returned at least in part to the reactor, preferably introducing it directly into the liquid phase of the reactor, via a separate plunge line or via the plunge line for feeding the reactor with LAA and LEA compounds.
• part of the liquid flow condensed in the partial condenser, containing polymerization inhibitors at low concentration, is returned using a pump to the upper outlet of the partial condenser, so as to protect the equipment against a risk of polymerization inside the condenser.
• the residue stream recovered at the bottom of the reactor (6) is cooled, then eliminated in the form of a liquid of moderate viscosity, so that it can be transported without difficulty by pump, for example to a storage unit or to a storage unit. incineration.
• the feed stream composed of LAA and LEA is preheated through a heat exchanger before being introduced into the reactor.
• the thermal cracking reaction is carried out in batch mode.
• the feed stream is introduced directly into the liquid phase of the reactor, via a plunging pipe.
• the diagram of Figure 2 describes an embodiment of the process according to the same principle as that of Figure 1, specifying a possible implementation in the case where the reactor is heated by recirculation, using a pump P, of the reaction medium contained in the reactor (7), through a heat exchanger E3.
• the fraction of liquid flow (5) returned to the reactor will advantageously be recycled in the recirculation loop, preferably upstream of the exchanger E3, for example upstream of the recirculation pump P.
• reaction temperature is the temperature measured in the liquid contained in the liquid phase of the reactor R
• the "head temperature” is the temperature of the vapors measured at the outlet of the partial condenser E1 (stream 3)
• the "residence time” in the reactor is measured by the mass ratio of the useful volume of the reactor (volume of liquid phase in the reactor) over the feed rate of heavy goods (stream 1).
• topping ratio is the mass ratio of the flow rate of condensed flow at the outlet of the total condenser E2 (flow 4) on the feed flow rate (flow 1)
• useful recovery rate is the mass ratio of the sum of recoverable compounds (AA, AE and ethanol) collected in the distillate after total condensation (stream 4) on the heavy feed flow rate (stream 1).
• useful conversion is the mass ratio of the sum of the recoverable compounds (AA, AE and ethanol) generated by cracking and recovered in the completely condensed stream (stream 4), after subtracting the sum of these compounds present in the feed (stream 1), related to the feed rate of the reactor (fluxl) after subtracting the valuable compounds present in this flux.
• the "viscosity @ 100 ° C” is the viscosity value in Pa.s at a temperature of 100 ° C of the residue obtained at the bottom of the reactor (flow 6), measured using a Brookfield “CAP 1000+” viscometer of the cone-plane type, equipped with mobile No. 2, at a rotational speed of 750 rotations per minute.
• Example 1 Cracking with partial condensation and reflux of the condensed liquid in the gas overhead of the reactor
• the assembly consists of a glass reactor with a total volume of 1 liter, heated by oil recirculation through its double wall, equipped with a side outlet for the exit of the residue, ensuring a useful volume of liquid contained in the 240ml reactor.
• the reactor is equipped with an agitator, a temperature probe submerged in the liquid phase, a vertical pipe at the top, for the extraction of vapors, and a partial condenser. Partial condensation is provided by cooling the reaction vapors on a thermowell placed inside the vertical vapor extraction tube, in which oil circulates at a controlled temperature of 150 ° C. A temperature probe is used to measure the temperature of the non-condensed vapors at the outlet of the partial condenser. These uncondensed vapors are directed to a total condenser, consisting of a double-walled refrigerant circulated by water at 10 ° C. The liquid (distillate) is collected in a receiving flask and analyzed.
• the mounting elements in contact with the vapors, from their generation in the reactor to their entry into the second condenser, are heat insulated to reduce heat exchange with the outside. In this assembly, the fraction of vapor condensed in the partial condenser naturally flows back to the reactor.
• a mixture consisting of 60% by mass of heavy compounds originating from an AA production unit and 40% by mass of heavy compounds originating from an ethyl acrylate (AE) production unit is sent continuously into the reactor , with a flow rate of 70g / h. Under these conditions, the residence time is 3.4 hours.
• the feed mixture is essentially composed of valuable compounds (9% AA and less than 0.1% of EA and ethanol), heavy compounds derived from Michael (35.5% of AA dimer (AA2), 1 , 5% AA trimer (AA3), 3.3% 3-ethoxypropionic acid (AEP), 0.3% 3-hydroxypropionic acid (AHP), 6.2% ethyl 3- ethoxypropionate ( EPE), 6.7% ethyl 3-acryloxypropionate (APE), 0.5% 3- ethyl hydroxypropionate (HPE), and polymerization inhibitors (2.7% hydroquinone (HQ), 0.6% phenothiazine (PTZ)).
• Michael 35.5% of AA dimer (AA2), 1 , 5% AA trimer (AA3)
• AEP 3-ethoxypropionic acid
• AHP 3-hydroxypropionic acid
• EPE ethyl 3- ethoxypropionate
• APE 6.7% ethyl 3-acryloxypropionate
• HPE
• Example 1 after operation under stable conditions for more than 24 hours, the reaction temperature is 195 ° C and the temperature of the vapors leaving the partial condenser is 157 ° C.
• Table 1 summarizes the operating conditions and performance of these tests.
• Example 2 and 3 (comparative): (SF57-4 and SF58-4) Cracking without condensation, according to the prior art
• reaction temperature of test 3 carried out with a residence time of 6 h in comparison with test 2 carried out with a residence time of 3.5 h, is much lower, to obtain a residue of similar cracking.
• the viscosity of the residue increases sharply and makes it difficult to transport the liquid.
• the consequence of the Lower usable temperature at higher residence time without an exaggerated increase in viscosity is a significant reduction in cracking performance.
• Example 4 Partial condensation of a flow resulting from the cracking reaction of heavy AA and heavy AE
• a liquid mixture resulting from the total condensation of a cracking operation of a mixture of LAA (60%) and LAE (40 %), is vaporized and partially condensed in a shell and tube condenser at a temperature of 160 ° C.
• a condensed liquid stream is obtained which represents 30% by mass of the condenser feed stream.
• This liquid condensate has a composition representative of the reflux (5) of Figure 1, containing 35.4% AA, 0.3% EA, 4.4% AA2, 0.4% AA3, 11.5% EPA, 22% EPE, 6.2% EPA, 0.1% HPE, 0.3% HQ, 0.04% PTZ.
• the "useful conversion rate” is the mass ratio of the sum of the recoverable compounds (AA, AE and ethanol) generated by cracking and recovered in the completely condensed stream (stream 4), after subtraction of the sum of these compounds present in the feed (stream 1) and in the recycled stream (stream 5), related to the feed rate of the reactor (fluxl) after subtracting the valuable compounds present in this stream (1).
• the experimental set-up is the same as that of Example 1, except that the vapors generated during the cracking reaction are sent directly into the total condenser (E2) and a flow rate of condensate flow obtained in Example 3 is introduced by plunging rod into the reactor, in addition to the supply of LAA and LAE.
• This device makes it possible to rigorously simulate the recycling of the condensed cracker stream at a temperature of 160 ° C, according to the ratio of recycling flow rate / LAA and LAE feed flow rate of 22% expected corresponding to a vapor condensation rate. by 30%.
• Example 5 the reactor is fed with the mixture of LAA and LAE described in Example 1, at a flow rate of 80 g / h, and the flow of condensate from Example 3 (stream 5) is introduced into the reactor, by a rod immersed in the liquid phase, at a flow rate of 17.6 g / h.
• Example 8 the feed flow rate (1) of LAA and LAE is 40 g / h and the flow rate of recycled condensate (5) is 8.8 g / h.
• the samples of the flow coming from the total condenser E2 (flow 4) and the residue at the bottom of the reactor (flow 6) are taken and analyzed.
• Example 9 the LAA and LAE feed rate of Example 9 (residence time of 3 h) is 80 g / h, and that of Example 10 (residence time of 3 h) is the same as that of Example 8, ie 40 g / h.
• Tests 9 and 10 make it possible to compare the cracking performance at different residence times.
• the comparison of tests 7 and 8 shows that the cracking reaction temperature must be reduced when the residence time is higher, but the recovery performance still remains much better under these time conditions.
• higher residence time (test 8) than in test 9 which was carried out according to the prior art under operating conditions which are, however, more favorable, with a lower residence time, with a viscosity of the residue which is also lower.
• This therefore shows that the process according to the invention makes it possible to continue to recover much more noble product from the same mixture of LAA-LAE, even when the flow rate of heavy goods to be treated is lower for reasons of fluctuation of the speeds. production of AA and ester workshops which lead to an increase in residence time.

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• 2020
  • 2020-05-19 FR FR2005057A patent/FR3110571B1/fr active Active
• 2021
  • 2021-05-11 EP EP21731260.2A patent/EP4139273B1/de active Active
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